THE MAGMATIC TO HYDROTHERMAL TRANSITION AND ITS BEARING ON ORE-FORMING SYSTEMS

Abstract

The exsolution of volatile phases from silicate magmas controls physical and chemical magma properties and influences large-scale geologic phenomena and processes having major societal and economic implications including the release of climate-altering gases to the atmosphere, the explosivity of volcanic eruptions, hydrothermal alteration, and the generation of magmatic–hydrothermal mineralization. These volatile phases exsolve from a wide variety of magmas and cover a very broad spectrum of compositions.The transition from the orthomagmatic to the hydrothermal stages has important bearing on these fundamentally important geologic phenomena, and this report summarizes the published results of a dozen scientific investigations on the magmatic–hydrothermal transition as applied to volcanic eruption and magmatic–hydrothermal mineralization. These studies involve a variety of analytical and experimental methodologies, and many focus on fluid and melt inclusions from mineralized magmatic systems. A primary goal of each study is to better understand the role of magmatic volatiles and the importance of the magmatic–hydrothermal transition on these geologic processes.